1. Field of the Invention
The invention relates to an apparatus for reducing the roughness and abrasive shedding of coated tapes by means of a rotating polishing element having a structured circumferential surface.
Coated tapes of the type which are xe2x80x9croughxe2x80x9d and cause abrasive shedding have a coating with a binder which comprises, for example, a polymer softer than PVC.
If such coated tapes are operated in equipment sensitive to abrasively shed material in such a way that these tapes come into contact with surfaces of fixed or moving parts of the equipment, malfunctions may occur as a result of deposition or accumulation of the abrasively shed material.
2. Description of the Related Art
A number of apparatuses and/or methods are known in which the surface of flexible tape-like material webs, for example of magnetic recording media are treated.
U.S. Pat. No. 5,012,548 discloses an apparatus for cleaning magnetic tapes having a rotatable cleaning element with hard, sharpedged inserts embedded in the circumference of a softer structure and airflow openings which are connected to a vacuum source. The tape is brought into contact to the blades and the cleaning element is rotated at a speed so that the tape passing over the cleaning element slips relative to the element.
U.S. Pat. No. 5,658,618 describes a further method of surface treatment. The essential feature of this method is that the abrasive coated surface of the material web is treated with itself, i.e. once again with a coated abrasive surface, by passing the web in the apparatus in such a way that, under predetermined conditions, the surfaces touch one another or come into frictional contact with one another over a certain length. The web movement is in opposite directions in the contact zone so that the resulting speed of the two surfaces relative to one another is twice the web speed. The treatment takes place simultaneously on the two surfaces: first, the surface which has been unwound last and is still untreated comes into contact with a previously treated surface which then itself becomes the surface treated once and, after deflection, comes into contact with a new surface not yet treated. Each of the two surfaces thus treats the other, actually resulting in a marked reduction in the abrasiveness. The dust formed in the frictional treatment must be extracted by a cleaning unit.
It is consequently an object of the present invention to remove such abrasively shed material from coated tapes which are intended for use in equipment of the type described without having dust-like residues to be removed by additional cleaning means.
We have found that this object is achieved according to the invention with an apparatus for reducing the roughness and abrasive shedding of coated tapes by means of a rotating polishing element having a structured circumferential surface, by means of a thread-like structure provided on the circumference of the polishing element.
Consequently, when the coating surface is taken past the circumferential structure mentioned, its roughness is reduced by grinding away the the peaks of the surface roughness and, surprisingly, at the same time the abrasively shed material is removed from the surface, which was not possible to achieve by cleaning alone.
In a partical refinement, the polishing element is a cylinder of which the height corresponds at least to the width of the coated tape, and in particular is twice the width.
This ensures simple production of the polishing element and provides an adequate contact surface for the coated tape.
The circumferential structure of the cylinder may expediently substantially comprise coaxially arranged grooves, which may also have thread-like forms and may also be arranged with a minimum pitch of 0.16 mm.
To increase the effectiveness of the polishing element, there are advantageously also axially arranged grooves on the cylinder circumference.
The axial grooves may be formed with a V form, which encloses in particular an angle of 112xc2x0, but they may also have a sawtooth form, which may enclose in particular an angle of 63xc2x0.
The number of coaxial grooves may lie between about 1 and 20 and should be about 10 to achieve optimum results.
The coaxial grooves may have substantially a V form and the ridges in between may have a flank width of 0.1 mm at the circumferential surface of the cylinder.
The material of the cylinder circumference expediently comprises hardened steel. However, it may also advantageously comprise oxide ceramic or hard metal alloy.
The material of the cylinder circumference should have a hardness of at least 60 Rockwell.